Use table extension

Use table extension

Use table extension

Table extension is a data archiving technique used to preserve instance performance
and avert risk associated with querying growing data sets. To do this, table extension
separates data sets into multiple tables based on date.

Before you begin

Role required: adminThis example outlines how to use table extension.

About this task

Note: Deployment of this plugin should be
executed in partnership with a ServiceNow
representative.

The administrator of the process is given the ability to specify time parameter
(duration) of the process. Although the administrator can also specify the number of
tables (rotations), this is not the best practice. After the last table in a
rotation is written, new tables are added and old tables are archived. Using table
extension, tables are never overwritten.

An advantage of table extension is to partition data across tables. It also allows
you to archive data while ensuring that tables stay reasonably-sized. The working
set of data is reduced when a date is known for the query.

The disadvantage is that table extension equires a union query when you query for a
time range that spans multiple tables. Union queries are less efficient than queries
against a single table.

A good practice is to use table extension when you have sequentially-written tables
or insert-only type tables (there are exceptions to this parameter). Table extension
is also useful in tables where data is needed for long periods of time.

The following example describes how to set table extension for the [sys_audit]
table.

Procedure

Navigate to System Definition > Table Rotations.

Click New.

Enter the following information.

Field

Action

Name

Enter the name of the table to apply the action. In
this example, the table is [sys_audit].

Duration

Enter the overall duration for the action. 30 days is
the duration in this example.